Last week, I had the pleasure of attending the gargantuan U.S. Science & Engineering Festival in Washington, D.C., with my friends at Celestron — Kevin Kawai, Jason Mulek, and Brenda Abrica. While I was in town, I got a text message from an old friend, Geoff Chester of the U.S. Naval Observatory. “You really ought to stop by,” he said. And he was right. So Kevin and Brenda joined me, and on Monday morning, April 28, before we all headed to the airport, Geoff gave us a fantastic behind-the-scenes tour of one of the great astronomical institutions in America.

The U.S. Naval Observatory is located on the grounds of Observatory Circle, which also houses the vice president’s house, located near the British Embassy, off Massachusetts Avenue, northwest of the city center. I hadn’t been there in years, probably around 1990, when I visited my deep-sky observing friend Brent Archinal there (he has long been in Flagstaff), and I vividly recall having our car inspected by those look-underneath mirrors.

This time, Geoff Chester met us bright and early and played a terrific host, explaining everything we saw thoroughly and giving us some fantastic stories of people and events. We began by walking uphill to the main observatory building, passing the helipad used by the vice president, and walking inside to begin looking at a vast array of historic instruments.

One of the most amazing is a relatively simple instrument, the 6-inch transit circle, which for a century provided spectacularly accurate positions for objects transiting across the sky. It therefore produced the standard coordinate system based on precise measurements of countless stars and other objects. The scope was used from 1897 through 1995.

Years ago, I visited the Old Naval Observatory buildings and grounds down in the city, in the Foggy Bottom area, where I was thrilled to climb up through the same hatch where Abraham Lincoln passed to see celestial objects shown by the great astronomer Asaph Hall. The old observatory site has long been defunct and is now occupied by the Navy’s Bureau of Medicine and Surgery. The most famous telescope, which had been located down on Foggy Bottom until 1893, is the 26-inch “Great Equatorial” refractor, which has a Clark lens and was famously used by Asaph Hall to discover the moons of Mars, Phobos and Deimos, in 1877. What a thrill it is to stand beside this great telescope! We also had the pleasure of seeing the smaller instrument, the observatory’s 12-inch Clark refractor, which Geoff often uses for planetary imaging.

The observatory’s circular library is packed with historic stuff, including memorabilia of Asaph Hall, great USNO astronomers like Simon Newcomb, and even a relic of my past — issues of Deep Sky magazine. The fabulous library desk used by Asaph Hall now sometimes serves as a backdrop for morning television interviews with Vice President Joe Biden coming up from the house and sitting in the pleasant library.

Geoff also filled us in on many stories relating to showing some of the VPs some astronomical sights, usually with the 12-inch refractor and often accompanied by VIPs or by members of their families. Al Gore was a legend for being interested in astronomy and knowing quite a few of the basics, and Biden is the consummate Washington politician — a warm, people person who is always interested in scientific topics and remembers everyone’s family members and all sorts of little details.

We did enjoy peering out across the grounds and catching a glimpse of the high parts of the vice president’s house, which originally was the observatory superintendent’s quarters. We couldn’t tell whether or not Joe was home, but he was probably pretty busy even if so . . .

We concluded our gracious tour with Geoff by looking at the defining timekeeping mechanisms on Earth. (Sorry, Royal Greenwich Observatory.) The big array of some 30 cesium atomic clocks are no longer quite on the cutting edge. They’re still in use, but a newer generation of atomic clocks, rubidium fountain clocks, which look like giant stainless steel water heaters, are now on the job and are even more accurate. All the defining time signals, for the Internet and everything else, originate from these rooms.

After our two-hour walk through USNO, we had to head to the airport and it was goodbye, Washington, for now.